Tip-1
Disk Clean Up
1)Click Start
2)Click run
3)Type Cleanmgr
4)Click OK
5)Select C: Drive
6)Click Ok
7)Check all the options in Files to delete
8)Click Ok
Tip: 2
Disk Defragment:
1)Open My Computer
2)Right Click C: Drive- Properties
3)Select Tools Tab
4)Click Defragment Now
Sunday, August 16, 2009
Types of Disk Formatting
There are two types of formats to consider:
-Physical, or low-level
-Logical, or high-level
When you format a floppy disk, the DOS FORMAT command performs both kinds of formats simultaneously. To format a hard disk, however, you must perform the operations separately. Moreover, a hard disk requires a third step, between the two formats, in which the partitioning information is written to the disk. Partitioning is required because a hard disk is designed to be used with more than one operating system. Separating the physical format in a way that is always the same, regardless of the operating system being used and regardless of the high-level format (which would be different for each operating system), makes possible the use of multiple operating systems on one hard drives. The partitioning step allows more than one type of operating system to use a single hard disk or a single DOS to use the disk as several volumes or logical drives. A volume or logical drive is anything to which DOS assigns a drive letter.
Consequently, formatting a hard disk involves three steps:
1. Low-Level Formatting (LLF)
2. Partitioning
3. High-Level Formatting (HLF)
During a low-level format, the disk's tracks are divided into a specific number of sectors. The sector header and trailer information is recorded, as are intersected and inter track gaps. Each sector's data area is filled with a dummy byte value or test pattern of values. For floppy disks, the number of sectors recorded on each track depends on the type of disk and drive; for hard disks, the number of sectors per track depends on the drive and controller interface.
The original ST-506/412 MFM controllers always placed 17 sectors per track on a disk. ST-506/412 controllers with RLL encoding increase the number of sectors on a drive to 25 or 26 sectors per track. ESDI drives can have 32 or more sectors per track. IDE drives simply are drives with built-in controllers, and depending on exactly what type of controller design is built in, the number of sectors per track can range from 17 to 100 or more. SCSI drives essentially are the same as IDE drives internally with an added SCSI Bus Adapter circuit, meaning that they also have some type of built-in controller; and like IDE drives, SCSI drives can have practically any number of sectors per track, depending on what controller design was used.
Virtually all IDE and SCSI drives use a technique called Zoned Recording, which writes a variable number of sectors per track. The outermost tracks hold more sectors than the inner tracks do, because they are longer. Because of limitations in the PC BIOS, these drives still have to act as though they have a fixed number of sectors per track. This situation is handled by translation algorithms that are implemented in the controller.
Multiple Zone Recording:
One way to increase the capacity of a hard drive is to format more sectors on the outer cylinders than on the inner ones. Because they have a larger circumference, the outer cylinders can hold more data. Drives without Zoned Recording store the same amount of data on every cylinder, even though the outer cylinders may be twice as long as the inner cylinders. The result is wasted storage capacity, because the disk media must be capable of storing data reliably at the same density as on the inner cylinders. With older ST-506/412 and ESDI controllers, unfortunately, the number of sectors per track was fixed; drive capacity, therefore, was limited by the density capability of the innermost (shortest) track.
In a Zoned Recording, the cylinders are split into groups called zones, with each successive zone having more and more sectors per track as you move out from the inner radius of the disk. All the cylinders in a particular zone have the same number of sectors per track. The number of zones varies with specific drives, but most drives have 10 or more zones.
Another effect of Zoned Recording is that transfer speeds vary depending on what zone the heads are in. Because there are more sectors in the outer zones, and the rotational speed is always the same, the transfer rate will be highest.
Drives with separate controllers could not handle zoned recordings because there was no standard way to communicate information about the zones from the drive to the controller. With SCSI and IDE disks, it became possible to format individual tracks with different numbers of sectors, due to the fact that these drives have the disk controller built in. The built-in controllers on these drives can be made fully aware of the zoning that is used. These built-in controllers must then also translate the physical Cylinder, Head, and Sector numbers to logical Cylinder, Head, and Sector numbers so that the drive has the appearance of having the same number of sectors on each track. The PC BIOS was designed to handle only a single number of specific sectors per track throughout the entire drive, meaning that zoned drives always must run under a sector translation scheme.
The use of Zoned Recording has allowed drive manufacturers to increase the capacity of their hard drives by between 20 percent and 50 percent compared with a fixed-sector-per-track arrangement. Virtually all IDE and SCSI drives today use Zoned Recording.
Partitioning:
Partitioning segments the drive into areas, called partitions, that can hold a particular operating system's file system. Today, PC operating systems use four common file systems:
1)FAT (File Allocation Table). The standard file system used by DOS, Windows 95 (Non-OSR2 release), OS/2, and Windows NT. FAT partitions support file names of 11 characters maximum (8+3 character extension) under DOS, and 255 characters under Windows 95 or NT 4.0 or later versions. Under the standard FAT system, 12-bit or 16-bit numbers are used to identify allocation units, resulting in a maximum volume size of 2G.
2)FAT32 (File Allocation Table, 32-bit). An optional file system used by Windows 95 OSR2 (also called OEM Service Release 2 or Windows 95B) or later versions. Under FAT32, file allocation units are stored as 32-bit numbers, allowing for a single volume of 2T or 2,048G in size. FAT-32 support will likely be added to Windows NT in the future.
3)HPFS (High Performance File System). A file system that's accessible only under OS/2 and Windows NT 3.51 or earlier. DOS applications running under OS/2 or Windows NT, or via a network, can access files in HPFS partitions, but straight DOS cannot. File names can be 256 characters long, and volume size is limited to 8G.
4)NTFS (Windows NT File System). A UNIX-like file system that's accessible only under Windows NT. DOS cannot access these partitions, but DOS applications running under Windows NT or accessing a Windows NT volume from the network can. File names can be 256 characters long, and volume size is limited to 8G.
Of these four file systems, the FAT file system still is by far the most popular (and recommended). The main problem with the original 16-bit FAT file system is that disk space is used in groups of sectors called allocation units or clusters. Because the total number of clusters is limited to 65,536 (the most that can be represented with a 16-bit number), larger drives required that the disk be broken into larger clusters. The larger cluster sizes required cause disk space to be used inefficiently. FAT-32 solves this problem by allowing the disk to be broken up into over 4 billion clusters, so the cluster sizes can be kept smaller. Most FAT-32 and NTFS volumes use 4K clusters.
High-Level Format:
During the high-level format, the operating system (such as DOS, OS/2, or Windows) writes the structures necessary for managing files and data. FAT partitions have a Volume Boot Sector (VBS), a file allocation table (FAT), and a root directory on each formatted logical drive. These data structures (discussed in detail in Chapter 22, "Operating Systems Software and Troubleshooting") enable the operating system to manage the space on the disk, keep track of files, and even manage defective areas so that they do not cause problems.
High-level formatting is not really formatting, but creating a table of contents for the disk. In low-level formatting, which is the real formatting, tracks and sectors are written on the disk. As mentioned, the DOS FORMAT command can perform both low-level and high-level format operations on a floppy disk, but it performs only the high-level format for a hard disk. Hard disk low-level formats require a special utility, usually supplied by the disk-controller manufacturer.
There are two types of formats to consider:
-Physical, or low-level
-Logical, or high-level
When you format a floppy disk, the DOS FORMAT command performs both kinds of formats simultaneously. To format a hard disk, however, you must perform the operations separately. Moreover, a hard disk requires a third step, between the two formats, in which the partitioning information is written to the disk. Partitioning is required because a hard disk is designed to be used with more than one operating system. Separating the physical format in a way that is always the same, regardless of the operating system being used and regardless of the high-level format (which would be different for each operating system), makes possible the use of multiple operating systems on one hard drives. The partitioning step allows more than one type of operating system to use a single hard disk or a single DOS to use the disk as several volumes or logical drives. A volume or logical drive is anything to which DOS assigns a drive letter.
Consequently, formatting a hard disk involves three steps:
1. Low-Level Formatting (LLF)
2. Partitioning
3. High-Level Formatting (HLF)
During a low-level format, the disk's tracks are divided into a specific number of sectors. The sector header and trailer information is recorded, as are intersected and inter track gaps. Each sector's data area is filled with a dummy byte value or test pattern of values. For floppy disks, the number of sectors recorded on each track depends on the type of disk and drive; for hard disks, the number of sectors per track depends on the drive and controller interface.
The original ST-506/412 MFM controllers always placed 17 sectors per track on a disk. ST-506/412 controllers with RLL encoding increase the number of sectors on a drive to 25 or 26 sectors per track. ESDI drives can have 32 or more sectors per track. IDE drives simply are drives with built-in controllers, and depending on exactly what type of controller design is built in, the number of sectors per track can range from 17 to 100 or more. SCSI drives essentially are the same as IDE drives internally with an added SCSI Bus Adapter circuit, meaning that they also have some type of built-in controller; and like IDE drives, SCSI drives can have practically any number of sectors per track, depending on what controller design was used.
Virtually all IDE and SCSI drives use a technique called Zoned Recording, which writes a variable number of sectors per track. The outermost tracks hold more sectors than the inner tracks do, because they are longer. Because of limitations in the PC BIOS, these drives still have to act as though they have a fixed number of sectors per track. This situation is handled by translation algorithms that are implemented in the controller.
Multiple Zone Recording:
One way to increase the capacity of a hard drive is to format more sectors on the outer cylinders than on the inner ones. Because they have a larger circumference, the outer cylinders can hold more data. Drives without Zoned Recording store the same amount of data on every cylinder, even though the outer cylinders may be twice as long as the inner cylinders. The result is wasted storage capacity, because the disk media must be capable of storing data reliably at the same density as on the inner cylinders. With older ST-506/412 and ESDI controllers, unfortunately, the number of sectors per track was fixed; drive capacity, therefore, was limited by the density capability of the innermost (shortest) track.
In a Zoned Recording, the cylinders are split into groups called zones, with each successive zone having more and more sectors per track as you move out from the inner radius of the disk. All the cylinders in a particular zone have the same number of sectors per track. The number of zones varies with specific drives, but most drives have 10 or more zones.
Another effect of Zoned Recording is that transfer speeds vary depending on what zone the heads are in. Because there are more sectors in the outer zones, and the rotational speed is always the same, the transfer rate will be highest.
Drives with separate controllers could not handle zoned recordings because there was no standard way to communicate information about the zones from the drive to the controller. With SCSI and IDE disks, it became possible to format individual tracks with different numbers of sectors, due to the fact that these drives have the disk controller built in. The built-in controllers on these drives can be made fully aware of the zoning that is used. These built-in controllers must then also translate the physical Cylinder, Head, and Sector numbers to logical Cylinder, Head, and Sector numbers so that the drive has the appearance of having the same number of sectors on each track. The PC BIOS was designed to handle only a single number of specific sectors per track throughout the entire drive, meaning that zoned drives always must run under a sector translation scheme.
The use of Zoned Recording has allowed drive manufacturers to increase the capacity of their hard drives by between 20 percent and 50 percent compared with a fixed-sector-per-track arrangement. Virtually all IDE and SCSI drives today use Zoned Recording.
Partitioning:
Partitioning segments the drive into areas, called partitions, that can hold a particular operating system's file system. Today, PC operating systems use four common file systems:
1)FAT (File Allocation Table). The standard file system used by DOS, Windows 95 (Non-OSR2 release), OS/2, and Windows NT. FAT partitions support file names of 11 characters maximum (8+3 character extension) under DOS, and 255 characters under Windows 95 or NT 4.0 or later versions. Under the standard FAT system, 12-bit or 16-bit numbers are used to identify allocation units, resulting in a maximum volume size of 2G.
2)FAT32 (File Allocation Table, 32-bit). An optional file system used by Windows 95 OSR2 (also called OEM Service Release 2 or Windows 95B) or later versions. Under FAT32, file allocation units are stored as 32-bit numbers, allowing for a single volume of 2T or 2,048G in size. FAT-32 support will likely be added to Windows NT in the future.
3)HPFS (High Performance File System). A file system that's accessible only under OS/2 and Windows NT 3.51 or earlier. DOS applications running under OS/2 or Windows NT, or via a network, can access files in HPFS partitions, but straight DOS cannot. File names can be 256 characters long, and volume size is limited to 8G.
4)NTFS (Windows NT File System). A UNIX-like file system that's accessible only under Windows NT. DOS cannot access these partitions, but DOS applications running under Windows NT or accessing a Windows NT volume from the network can. File names can be 256 characters long, and volume size is limited to 8G.
Of these four file systems, the FAT file system still is by far the most popular (and recommended). The main problem with the original 16-bit FAT file system is that disk space is used in groups of sectors called allocation units or clusters. Because the total number of clusters is limited to 65,536 (the most that can be represented with a 16-bit number), larger drives required that the disk be broken into larger clusters. The larger cluster sizes required cause disk space to be used inefficiently. FAT-32 solves this problem by allowing the disk to be broken up into over 4 billion clusters, so the cluster sizes can be kept smaller. Most FAT-32 and NTFS volumes use 4K clusters.
High-Level Format:
During the high-level format, the operating system (such as DOS, OS/2, or Windows) writes the structures necessary for managing files and data. FAT partitions have a Volume Boot Sector (VBS), a file allocation table (FAT), and a root directory on each formatted logical drive. These data structures (discussed in detail in Chapter 22, "Operating Systems Software and Troubleshooting") enable the operating system to manage the space on the disk, keep track of files, and even manage defective areas so that they do not cause problems.
High-level formatting is not really formatting, but creating a table of contents for the disk. In low-level formatting, which is the real formatting, tracks and sectors are written on the disk. As mentioned, the DOS FORMAT command can perform both low-level and high-level format operations on a floppy disk, but it performs only the high-level format for a hard disk. Hard disk low-level formats require a special utility, usually supplied by the disk-controller manufacturer.
Types of Disk Formatting
Types of Disk Formatting
There are two types of formats to consider:
-Physical, or low-level
-Logical, or high-level
When you format a floppy disk, the DOS FORMAT command performs both kinds of formats simultaneously. To format a hard disk, however, you must perform the operations separately. Moreover, a hard disk requires a third step, between the two formats, in which the partitioning information is written to the disk. Partitioning is required because a hard disk is designed to be used with more than one operating system. Separating the physical format in a way that is always the same, regardless of the operating system being used and regardless of the high-level format (which would be different for each operating system), makes possible the use of multiple operating systems on one hard drives. The partitioning step allows more than one type of operating system to use a single hard disk or a single DOS to use the disk as several volumes or logical drives. A volume or logical drive is anything to which DOS assigns a drive letter.
Consequently, formatting a hard disk involves three steps:
1. Low-Level Formatting (LLF)
2. Partitioning
3. High-Level Formatting (HLF)
During a low-level format, the disk's tracks are divided into a specific number of sectors. The sector header and trailer information is recorded, as are intersected and inter track gaps. Each sector's data area is filled with a dummy byte value or test pattern of values. For floppy disks, the number of sectors recorded on each track depends on the type of disk and drive; for hard disks, the number of sectors per track depends on the drive and controller interface.
The original ST-506/412 MFM controllers always placed 17 sectors per track on a disk. ST-506/412 controllers with RLL encoding increase the number of sectors on a drive to 25 or 26 sectors per track. ESDI drives can have 32 or more sectors per track. IDE drives simply are drives with built-in controllers, and depending on exactly what type of controller design is built in, the number of sectors per track can range from 17 to 100 or more. SCSI drives essentially are the same as IDE drives internally with an added SCSI Bus Adapter circuit, meaning that they also have some type of built-in controller; and like IDE drives, SCSI drives can have practically any number of sectors per track, depending on what controller design was used.
Virtually all IDE and SCSI drives use a technique called Zoned Recording, which writes a variable number of sectors per track. The outermost tracks hold more sectors than the inner tracks do, because they are longer. Because of limitations in the PC BIOS, these drives still have to act as though they have a fixed number of sectors per track. This situation is handled by translation algorithms that are implemented in the controller.
Multiple Zone Recording:
One way to increase the capacity of a hard drive is to format more sectors on the outer cylinders than on the inner ones. Because they have a larger circumference, the outer cylinders can hold more data. Drives without Zoned Recording store the same amount of data on every cylinder, even though the outer cylinders may be twice as long as the inner cylinders. The result is wasted storage capacity, because the disk media must be capable of storing data reliably at the same density as on the inner cylinders. With older ST-506/412 and ESDI controllers, unfortunately, the number of sectors per track was fixed; drive capacity, therefore, was limited by the density capability of the innermost (shortest) track.
In a Zoned Recording, the cylinders are split into groups called zones, with each successive zone having more and more sectors per track as you move out from the inner radius of the disk. All the cylinders in a particular zone have the same number of sectors per track. The number of zones varies with specific drives, but most drives have 10 or more zones.
Another effect of Zoned Recording is that transfer speeds vary depending on what zone the heads are in. Because there are more sectors in the outer zones, and the rotational speed is always the same, the transfer rate will be highest.
Drives with separate controllers could not handle zoned recordings because there was no standard way to communicate information about the zones from the drive to the controller. With SCSI and IDE disks, it became possible to format individual tracks with different numbers of sectors, due to the fact that these drives have the disk controller built in. The built-in controllers on these drives can be made fully aware of the zoning that is used. These built-in controllers must then also translate the physical Cylinder, Head, and Sector numbers to logical Cylinder, Head, and Sector numbers so that the drive has the appearance of having the same number of sectors on each track. The PC BIOS was designed to handle only a single number of specific sectors per track throughout the entire drive, meaning that zoned drives always must run under a sector translation scheme.
The use of Zoned Recording has allowed drive manufacturers to increase the capacity of their hard drives by between 20 percent and 50 percent compared with a fixed-sector-per-track arrangement. Virtually all IDE and SCSI drives today use Zoned Recording.
Partitioning:
Partitioning segments the drive into areas, called partitions, that can hold a particular operating system's file system. Today, PC operating systems use four common file systems:
1)FAT (File Allocation Table). The standard file system used by DOS, Windows 95 (Non-OSR2 release), OS/2, and Windows NT. FAT partitions support file names of 11 characters maximum (8+3 character extension) under DOS, and 255 characters under Windows 95 or NT 4.0 or later versions. Under the standard FAT system, 12-bit or 16-bit numbers are used to identify allocation units, resulting in a maximum volume size of 2G.
2)FAT32 (File Allocation Table, 32-bit). An optional file system used by Windows 95 OSR2 (also called OEM Service Release 2 or Windows 95B) or later versions. Under FAT32, file allocation units are stored as 32-bit numbers, allowing for a single volume of 2T or 2,048G in size. FAT-32 support will likely be added to Windows NT in the future.
3)HPFS (High Performance File System). A file system that's accessible only under OS/2 and Windows NT 3.51 or earlier. DOS applications running under OS/2 or Windows NT, or via a network, can access files in HPFS partitions, but straight DOS cannot. File names can be 256 characters long, and volume size is limited to 8G.
4)NTFS (Windows NT File System). A UNIX-like file system that's accessible only under Windows NT. DOS cannot access these partitions, but DOS applications running under Windows NT or accessing a Windows NT volume from the network can. File names can be 256 characters long, and volume size is limited to 8G.
Of these four file systems, the FAT file system still is by far the most popular (and recommended). The main problem with the original 16-bit FAT file system is that disk space is used in groups of sectors called allocation units or clusters. Because the total number of clusters is limited to 65,536 (the most that can be represented with a 16-bit number), larger drives required that the disk be broken into larger clusters. The larger cluster sizes required cause disk space to be used inefficiently. FAT-32 solves this problem by allowing the disk to be broken up into over 4 billion clusters, so the cluster sizes can be kept smaller. Most FAT-32 and NTFS volumes use 4K clusters.
High-Level Format:
During the high-level format, the operating system (such as DOS, OS/2, or Windows) writes the structures necessary for managing files and data. FAT partitions have a Volume Boot Sector (VBS), a file allocation table (FAT), and a root directory on each formatted logical drive. These data structures (discussed in detail in Chapter 22, "Operating Systems Software and Troubleshooting") enable the operating system to manage the space on the disk, keep track of files, and even manage defective areas so that they do not cause problems.
High-level formatting is not really formatting, but creating a table of contents for the disk. In low-level formatting, which is the real formatting, tracks and sectors are written on the disk. As mentioned, the DOS FORMAT command can perform both low-level and high-level format operations on a floppy disk, but it performs only the high-level format for a hard disk. Hard disk low-level formats require a special utility, usually supplied by the disk-controller manufacturer.
There are two types of formats to consider:
-Physical, or low-level
-Logical, or high-level
When you format a floppy disk, the DOS FORMAT command performs both kinds of formats simultaneously. To format a hard disk, however, you must perform the operations separately. Moreover, a hard disk requires a third step, between the two formats, in which the partitioning information is written to the disk. Partitioning is required because a hard disk is designed to be used with more than one operating system. Separating the physical format in a way that is always the same, regardless of the operating system being used and regardless of the high-level format (which would be different for each operating system), makes possible the use of multiple operating systems on one hard drives. The partitioning step allows more than one type of operating system to use a single hard disk or a single DOS to use the disk as several volumes or logical drives. A volume or logical drive is anything to which DOS assigns a drive letter.
Consequently, formatting a hard disk involves three steps:
1. Low-Level Formatting (LLF)
2. Partitioning
3. High-Level Formatting (HLF)
During a low-level format, the disk's tracks are divided into a specific number of sectors. The sector header and trailer information is recorded, as are intersected and inter track gaps. Each sector's data area is filled with a dummy byte value or test pattern of values. For floppy disks, the number of sectors recorded on each track depends on the type of disk and drive; for hard disks, the number of sectors per track depends on the drive and controller interface.
The original ST-506/412 MFM controllers always placed 17 sectors per track on a disk. ST-506/412 controllers with RLL encoding increase the number of sectors on a drive to 25 or 26 sectors per track. ESDI drives can have 32 or more sectors per track. IDE drives simply are drives with built-in controllers, and depending on exactly what type of controller design is built in, the number of sectors per track can range from 17 to 100 or more. SCSI drives essentially are the same as IDE drives internally with an added SCSI Bus Adapter circuit, meaning that they also have some type of built-in controller; and like IDE drives, SCSI drives can have practically any number of sectors per track, depending on what controller design was used.
Virtually all IDE and SCSI drives use a technique called Zoned Recording, which writes a variable number of sectors per track. The outermost tracks hold more sectors than the inner tracks do, because they are longer. Because of limitations in the PC BIOS, these drives still have to act as though they have a fixed number of sectors per track. This situation is handled by translation algorithms that are implemented in the controller.
Multiple Zone Recording:
One way to increase the capacity of a hard drive is to format more sectors on the outer cylinders than on the inner ones. Because they have a larger circumference, the outer cylinders can hold more data. Drives without Zoned Recording store the same amount of data on every cylinder, even though the outer cylinders may be twice as long as the inner cylinders. The result is wasted storage capacity, because the disk media must be capable of storing data reliably at the same density as on the inner cylinders. With older ST-506/412 and ESDI controllers, unfortunately, the number of sectors per track was fixed; drive capacity, therefore, was limited by the density capability of the innermost (shortest) track.
In a Zoned Recording, the cylinders are split into groups called zones, with each successive zone having more and more sectors per track as you move out from the inner radius of the disk. All the cylinders in a particular zone have the same number of sectors per track. The number of zones varies with specific drives, but most drives have 10 or more zones.
Another effect of Zoned Recording is that transfer speeds vary depending on what zone the heads are in. Because there are more sectors in the outer zones, and the rotational speed is always the same, the transfer rate will be highest.
Drives with separate controllers could not handle zoned recordings because there was no standard way to communicate information about the zones from the drive to the controller. With SCSI and IDE disks, it became possible to format individual tracks with different numbers of sectors, due to the fact that these drives have the disk controller built in. The built-in controllers on these drives can be made fully aware of the zoning that is used. These built-in controllers must then also translate the physical Cylinder, Head, and Sector numbers to logical Cylinder, Head, and Sector numbers so that the drive has the appearance of having the same number of sectors on each track. The PC BIOS was designed to handle only a single number of specific sectors per track throughout the entire drive, meaning that zoned drives always must run under a sector translation scheme.
The use of Zoned Recording has allowed drive manufacturers to increase the capacity of their hard drives by between 20 percent and 50 percent compared with a fixed-sector-per-track arrangement. Virtually all IDE and SCSI drives today use Zoned Recording.
Partitioning:
Partitioning segments the drive into areas, called partitions, that can hold a particular operating system's file system. Today, PC operating systems use four common file systems:
1)FAT (File Allocation Table). The standard file system used by DOS, Windows 95 (Non-OSR2 release), OS/2, and Windows NT. FAT partitions support file names of 11 characters maximum (8+3 character extension) under DOS, and 255 characters under Windows 95 or NT 4.0 or later versions. Under the standard FAT system, 12-bit or 16-bit numbers are used to identify allocation units, resulting in a maximum volume size of 2G.
2)FAT32 (File Allocation Table, 32-bit). An optional file system used by Windows 95 OSR2 (also called OEM Service Release 2 or Windows 95B) or later versions. Under FAT32, file allocation units are stored as 32-bit numbers, allowing for a single volume of 2T or 2,048G in size. FAT-32 support will likely be added to Windows NT in the future.
3)HPFS (High Performance File System). A file system that's accessible only under OS/2 and Windows NT 3.51 or earlier. DOS applications running under OS/2 or Windows NT, or via a network, can access files in HPFS partitions, but straight DOS cannot. File names can be 256 characters long, and volume size is limited to 8G.
4)NTFS (Windows NT File System). A UNIX-like file system that's accessible only under Windows NT. DOS cannot access these partitions, but DOS applications running under Windows NT or accessing a Windows NT volume from the network can. File names can be 256 characters long, and volume size is limited to 8G.
Of these four file systems, the FAT file system still is by far the most popular (and recommended). The main problem with the original 16-bit FAT file system is that disk space is used in groups of sectors called allocation units or clusters. Because the total number of clusters is limited to 65,536 (the most that can be represented with a 16-bit number), larger drives required that the disk be broken into larger clusters. The larger cluster sizes required cause disk space to be used inefficiently. FAT-32 solves this problem by allowing the disk to be broken up into over 4 billion clusters, so the cluster sizes can be kept smaller. Most FAT-32 and NTFS volumes use 4K clusters.
High-Level Format:
During the high-level format, the operating system (such as DOS, OS/2, or Windows) writes the structures necessary for managing files and data. FAT partitions have a Volume Boot Sector (VBS), a file allocation table (FAT), and a root directory on each formatted logical drive. These data structures (discussed in detail in Chapter 22, "Operating Systems Software and Troubleshooting") enable the operating system to manage the space on the disk, keep track of files, and even manage defective areas so that they do not cause problems.
High-level formatting is not really formatting, but creating a table of contents for the disk. In low-level formatting, which is the real formatting, tracks and sectors are written on the disk. As mentioned, the DOS FORMAT command can perform both low-level and high-level format operations on a floppy disk, but it performs only the high-level format for a hard disk. Hard disk low-level formats require a special utility, usually supplied by the disk-controller manufacturer.
Download videos from Youtube for free
Just a few days back I found some excellent videos on YouTube and wanted to download them to my PC.But as we know YouTube does not allow this facility. So I started searching for some lightweight app which can do this for me. And finally I found this YouTube Downloader which not only allows me to save those youtube videos on my hard disk but also I can convert them to any other file format.
How to use it??
All you need to do is copy the video URL you wish to download and paste it in the space asked which says "Enter the video URL".Once you press the "OK" button it will ask you where you want to save the video, select the location and you are done. Your video will be downloaded at the location selected by you. After that you can convert this video to any other format by using this software or you can use VLC player/FLV player to play the flv file.
To download this application visit the URL mentioned in the "For more details" header below.
OR
There is a simpler way to do this
just visit the site Downloadyoutubevideos and you can give the URL of the video there and download it without installing any software onto your PC.
For more details, visit http://youtubedownload.altervista.org/
How to use it??
All you need to do is copy the video URL you wish to download and paste it in the space asked which says "Enter the video URL".Once you press the "OK" button it will ask you where you want to save the video, select the location and you are done. Your video will be downloaded at the location selected by you. After that you can convert this video to any other format by using this software or you can use VLC player/FLV player to play the flv file.
To download this application visit the URL mentioned in the "For more details" header below.
OR
There is a simpler way to do this
just visit the site Downloadyoutubevideos and you can give the URL of the video there and download it without installing any software onto your PC.
For more details, visit http://youtubedownload.altervista.org/
What Is 3G
Hi friends,
This article is about the latest technology in mobile communications,3G yet to touch the Indian markets.
3G stands for 3rd generation technology.It can be viewed as an upgrade to the present technologies.This service offers very high data transfer both audio and video.
The Hierarchy of technologies are as follows:
1) 1G
This is the first one of this kind.It is analog in nature.
2) 2G
This is the first digital version.GSM(Global System for Mobile) and CDMA(Code Division Multiple Access) we use at present comes under this category.
3) 2.5G
An advancement to 2G and acts as a bridge between 2G and 3G.
4) 3G
5) 4G
This is the future.This already became a reality in some developed countries.
Technically, the main difference between 3G and 2G networks is how quickly data can be sent and received.For example an MP3 download in 2G takes in between 2-5 minutes where as in 3G,11 seconds-1.5 minutes.
Who can benefit from this?
Internet savvy people who need high data speeds will enjoy this technology.
Features:
This offers the combined services of Mobile phone,Laptop and TV.
Speed range is 144KB/sec-2MB/sec
Videoconferencing
Live TV
Global roaming
High-speed Web
Global positioning
Entertainment(Listening music,playing hi speed on line games,book tickets,watch streaming video etc)
News and Information
Apart from these,its applications are very helpful in areas like M-commerce.
This include trading shares,online transactions etc.
First precommercial version of 3G is lanched in May 2001 by NTT DoCoMo in Japan.In the same year,on October 1st,first commercial version was introduced.It became very popular.Since then many countries have been using its services.
What are the drawbacks of 3G
1.High bandwidth requirement
3G requires a bandwidth of 15-20 MH which is very high compared to 2G(30-200 KH).
2.High spectrum licencing fees
For any telecom company to offer this service,government have to allocate the spectrum.A spectrum simply determines the number of users a company can serve or offer this service.So if the spectrum allotted to a company is more,it can feed more number of customers.As the licencing fees is very high,companies find difficult to provide this technology.
3.Huge capital
All the infrastructure laid for 2G services becomes obsolete for 3G.Thus 3G requires seperate infrastucture which is costly.
4.Cost of upgradation
Upgrading to 3G will be an expensive affair.
3G is a truly a revolution in telecommunication.Lets wait and see to what extent Indian customers enjoy this one.
regards,
VIKAS ATHWAL
This article is about the latest technology in mobile communications,3G yet to touch the Indian markets.
3G stands for 3rd generation technology.It can be viewed as an upgrade to the present technologies.This service offers very high data transfer both audio and video.
The Hierarchy of technologies are as follows:
1) 1G
This is the first one of this kind.It is analog in nature.
2) 2G
This is the first digital version.GSM(Global System for Mobile) and CDMA(Code Division Multiple Access) we use at present comes under this category.
3) 2.5G
An advancement to 2G and acts as a bridge between 2G and 3G.
4) 3G
5) 4G
This is the future.This already became a reality in some developed countries.
Technically, the main difference between 3G and 2G networks is how quickly data can be sent and received.For example an MP3 download in 2G takes in between 2-5 minutes where as in 3G,11 seconds-1.5 minutes.
Who can benefit from this?
Internet savvy people who need high data speeds will enjoy this technology.
Features:
This offers the combined services of Mobile phone,Laptop and TV.
Speed range is 144KB/sec-2MB/sec
Videoconferencing
Live TV
Global roaming
High-speed Web
Global positioning
Entertainment(Listening music,playing hi speed on line games,book tickets,watch streaming video etc)
News and Information
Apart from these,its applications are very helpful in areas like M-commerce.
This include trading shares,online transactions etc.
First precommercial version of 3G is lanched in May 2001 by NTT DoCoMo in Japan.In the same year,on October 1st,first commercial version was introduced.It became very popular.Since then many countries have been using its services.
What are the drawbacks of 3G
1.High bandwidth requirement
3G requires a bandwidth of 15-20 MH which is very high compared to 2G(30-200 KH).
2.High spectrum licencing fees
For any telecom company to offer this service,government have to allocate the spectrum.A spectrum simply determines the number of users a company can serve or offer this service.So if the spectrum allotted to a company is more,it can feed more number of customers.As the licencing fees is very high,companies find difficult to provide this technology.
3.Huge capital
All the infrastructure laid for 2G services becomes obsolete for 3G.Thus 3G requires seperate infrastucture which is costly.
4.Cost of upgradation
Upgrading to 3G will be an expensive affair.
3G is a truly a revolution in telecommunication.Lets wait and see to what extent Indian customers enjoy this one.
regards,
VIKAS ATHWAL
Windows Short Cut Keys
Windows Short Cut Keys
task manager shortcut --> ctrl + shift + Esc.
ctrl + shift + clicking on hyperlink - opens page in new window (works in firefox too!)
ctrl + click a file and then draging it creates a copy of that file.
Windows key + e Opens Windows Explorer
Refresh webpage - Ctrl + R
Windows key + e Opens Windows Explorer
ctrl + shift + click a file and then draging it creates a shortcut of that file.
Alt + F4 close the window currently being used
or
If no windows are open then it brings you to a shut down screen
windows key + m minimizes all windows
windows key + f open the search window
windows key + L locks your station
F9-Volume Up
F10-Volume Down
windows key + pause/break key opens up system properties.
if multiple windows are opened:
alt + tab - will show the next page under the currently viewed one
List Of Important Days
This is the list of important days in india.
12-Jan National Youth Day.
15-Jan Army Day.
26-Jan India's Republic Day and International Customs day.
30-Jan Martyrs' Day
24-Feb Central Excise Day.
28-Feb National Science Day.
8-Mar International Women's Day.
15-Mar World Disabled Day.
21-Mar World Forestry Day.
21-Mar International Day for the Elimination of Racial Discrimination.
23-Mar World Meteorological Day.
5-Apr National Maritime Day.
7-Apr World Health Day.
18-Apr World Heritage Day.
22-Apr Earth Day.
1-May Workers Day (International LaborDay).
3-May Press Freedom Day.
May (2nd Sunday) Mother's Day.
8-May World Red Cross Day.
11-May National Technology Day.
15-May International Day of the Family.
17-May World Telecommunication Day.
24-May Commonwealth Day.
31-May Anti-Tobacco Day.
4-Jun International Day of Innocent Children Victims of Aggression.
5-Jun World Environment Day.
June(2nd Sunday) Fathers Day.
26-Jun International day against Drugabuse & Illicit Trafficking.
27-Jun World Diabetes Day.
6-Jul World Zoonoses Day.
11-Jul World Population Day.
3-Aug International Friendship Day.
6-Aug Hiroshima Day,
9-Aug Quit India Day and Nagasaki Day.
15-Aug Independence Day.
29-Aug National Sports Day.
5-Sep Teachers' Day.
8-Sep World Literacy Day.
16-Sep World Ozone Day.
21-Sep Alzheimer's Day.
26-Sep Day of the Deaf.
27-Sep World Tourism Day.
1-Oct International day of the Elderly
3-Oct World Habitat Day.
4-Oct World Animal Welfare Day.
8-Oct Indian Air Force Day.
9-Oct World Post Office day.
10-Oct National Post Day.
13-Oct UN International Day for Nationaldisaster reduction.
14-Oct World Standards Day.
15-Oct World White Cane Day( guiding theBlind).
16-Oct World Food Day.
24-Oct UN Day, World development information Day.
30-Oct World Thrift Day.
14-Nov Children's Day ( in India )
20-Nov Africa Industrialization Day.
29-Nov International Day of Solidarity with Palestinian People.
1-Dec World Aids Day.
4-Dec Navy Day.
7-Dec Armed Forces Flag Day.
10-Dec Human Right Day.
23-Dec Kisan Divas Farmer's Day).
12-Jan National Youth Day.
15-Jan Army Day.
26-Jan India's Republic Day and International Customs day.
30-Jan Martyrs' Day
24-Feb Central Excise Day.
28-Feb National Science Day.
8-Mar International Women's Day.
15-Mar World Disabled Day.
21-Mar World Forestry Day.
21-Mar International Day for the Elimination of Racial Discrimination.
23-Mar World Meteorological Day.
5-Apr National Maritime Day.
7-Apr World Health Day.
18-Apr World Heritage Day.
22-Apr Earth Day.
1-May Workers Day (International LaborDay).
3-May Press Freedom Day.
May (2nd Sunday) Mother's Day.
8-May World Red Cross Day.
11-May National Technology Day.
15-May International Day of the Family.
17-May World Telecommunication Day.
24-May Commonwealth Day.
31-May Anti-Tobacco Day.
4-Jun International Day of Innocent Children Victims of Aggression.
5-Jun World Environment Day.
June(2nd Sunday) Fathers Day.
26-Jun International day against Drugabuse & Illicit Trafficking.
27-Jun World Diabetes Day.
6-Jul World Zoonoses Day.
11-Jul World Population Day.
3-Aug International Friendship Day.
6-Aug Hiroshima Day,
9-Aug Quit India Day and Nagasaki Day.
15-Aug Independence Day.
29-Aug National Sports Day.
5-Sep Teachers' Day.
8-Sep World Literacy Day.
16-Sep World Ozone Day.
21-Sep Alzheimer's Day.
26-Sep Day of the Deaf.
27-Sep World Tourism Day.
1-Oct International day of the Elderly
3-Oct World Habitat Day.
4-Oct World Animal Welfare Day.
8-Oct Indian Air Force Day.
9-Oct World Post Office day.
10-Oct National Post Day.
13-Oct UN International Day for Nationaldisaster reduction.
14-Oct World Standards Day.
15-Oct World White Cane Day( guiding theBlind).
16-Oct World Food Day.
24-Oct UN Day, World development information Day.
30-Oct World Thrift Day.
14-Nov Children's Day ( in India )
20-Nov Africa Industrialization Day.
29-Nov International Day of Solidarity with Palestinian People.
1-Dec World Aids Day.
4-Dec Navy Day.
7-Dec Armed Forces Flag Day.
10-Dec Human Right Day.
23-Dec Kisan Divas Farmer's Day).
Saturday, August 15, 2009
शूकर इन्फ्लूएंजा
शूकर इन्फ्लूएंजा, जिसे एच1एन1 या स्वाइन फ्लू भी कहते हैं, विभिन्न शूकर इन्फ्लूएंजा विषाणुओं मे से किसी एक के द्वारा फैलाया गया संक्रमण है। शूकर इन्फ्लूएंजा विषाणु (SIV-एस.आई.वी), इन्फ्लूएंजा कुल के विषाणुओं का वह कोई भी उपभेद है, जो कि सूअरों की स्थानिकमारी के लिए उत्तरदायी है।[२] 2009 तक ज्ञात एस.आई.वी उपभेदों में इन्फ्लूएंजा सी और इन्फ्लूएंजा ए के उपप्रकार एच1एन1 (H1N1), एच1एन2 (H1N2), एच3एन1 (H3N1), एच3एन2 (H3N2) और एच2एन3 (H2N3) शामिल हैं। इस प्रकार का इन्फ्लूएंजा मनुष्यों और पक्षियों पर भी प्रभाव डालता है।
शूकर इन्फ्लूएंजा विषाणु का दुनिया भर के सुअरो मे पाया जाना आम है। इस विषाणु का सूअरों से मनुष्य मे संचरण आम नहीं है और हमेशा ही यह विषाणु मानव इन्फ्लूएंजा का कारण नहीं बनता, अक्सर रक्त में इसके विरुद्ध सिर्फ प्रतिपिंडों (एंटीबॉडी) का उत्पादन ही होता है। यदि इसका संचरण, मानव इन्फ्लूएंजा का कारण बनता है, तब इसे ज़ूनोटिक शूकर इन्फ्लूएंजा कहा जाता है। जो व्यक्ति नियमित रूप से सूअरों के सम्पर्क में रहते है उन्हें इस फ्लू के संक्रमण का जोखिम अधिक होता है। यदि एक संक्रमित सुअर का मांस ठीक से पकाया जाये तो इसके सेवन से संक्रमण का कोई खतरा नहीं होता।
२०वीं शताब्दी के मध्य मे, इन्फ्लूएंजा के उपप्रकारों की पहचान संभव हो गयी जिसके कारण, मानव मे इसके संचरण का सही निदान संभव हो पाया। तब से ऐसे केवल ५० संचरणों की पुष्टि की गई है। शूकर इन्फ्लूएंजा के यह उपभेद बिरले ही एक मानव से दूसरे मानव मे संचारित होते हैं। मानव में ज़ूनोटिक शूकर इन्फ्लूएंजा के लक्षण आम इन्फ्लूएंजा के लक्षणों के समान ही होते हैं, जैसे ठंड लगना, बुखार, गले में ख़राश, खाँसी, मांसपेशियों में दर्द, तेज सिर दर्द, कमजोरी और सामान्य बेचैनी।
अनुक्रम |
चिन्ह व लक्षण
सूअर में
सूअरों में इन्फ्लूएंजा संक्रमण के कारण ज्वर, सुस्ती, छींक, खाँसी, साँस लेने में कठिनाई, और भूख की कमी हो सकती है। कुछ मामलों में यह संक्रमण गर्भपात का कारण बन सकता है। हालांकि आमतौर पर मृत्यु सिर्फ 1-4% मामलों मे ही होती है। यह संक्रमण सूअर का वजन घटा और विकास को प्रभावित कर सकता है जो इनके पालको के आर्थिक नुकसान का कारण बन सकता है। संक्रमित सूअर का वजन 3 से 4 सप्ताह की अवधि के दौरान ५ से ६ किलोग्राम तक घट सकता है।
मनुष्यों में
मनुष्यों में शूकर इन्फ्लूएंजा का मुख्य लक्षण हैं: -
- ज्वर
- गले मे खरांश
- जुकाम
- खाँसी
- सिर व बदन दर्द
- जोड़ों में कठोरता
- उल्टी
- मूर्छा
- ठंड लगना
शूकर इन्फ्लूएंजा विषाणु का संचरण सीधे सूअरों से मनुष्यों मे कभी कभी संभव है, इस स्थित मे इसे जू़नोटिक शूकर इन्फ्लूएंजा कहा जाता है। 1958 से अभी तक सिर्फ 50 मामले ही रिपोर्ट हुये हैं जिनमे से सिर्फ ६ व्यक्तियों की ही मृत्यु हुई है। इन छह लोगों में से एक महिला गर्भवती थी, एक को ल्यूकिमिया था, एक को हॉजकिन रोग था और दो लोग पहले से स्वस्थ थे। भले ही यह प्रत्यक्ष मामले बहुत कम लगें पर वास्तविक संक्रमण की सही दर कहीं अधिक हो सकती है, क्योंकि ज्यादातर मामलों मे यह सामान्य रोग ही लगता है, और इस कारण इसे रिपोर्ट ही नहीं किया जाता।
वर्गीकरण
तीन वंशो के इन्फ्लूएंजा विषाणु जो कि मानव इन्फ्लूएंजा के लिए उत्तरदायी हैं मे से दो सूअरों में भी इन्फ्लूएंजा फैला सकते हैं, जिसमे से इन्फ्लूएंजा ए तो बहुत आम है पर इन्फ्लूएंजा सी यदा कदा ही पाया जाता है।[४]अभी तक इन्फ्लूएंजा बी को सूअरों में देखा नहीं गया है। इन्फ्लूएंजा ए और इन्फ्लूएंजा सी के भीतर मनुष्य और सूअरों में पाये जाने वाले उपभेद भिन्न होते हैं हालांकि रीअसोर्टमेंट के कारण उपभेदों मे बड़े पैमाने जीन का स्थानांतरण देखा गया है चाहें यह सूअर, पक्षी या मानव प्रजाति में उपस्थित हो।
इन्फ्लूएंजा सी
इन्फ्लूएंजा सी विषाणु, मानव और सूअरों दोनों को संक्रमित करता है लेकिन इसका संक्रमण पक्षियों मे नहीं होता।[५] अतीत मे भी इसका संचरण सूअरों और इंसानों के बीच हुआ है।[६]उदाहरण के लिए, इन्फ्लूएंजा सी के कारण जापान[७] और कैलिफोर्निया[७] में बच्चों के बीच इन्फ्लूएंजा का कम प्रभावी प्रकार फैला था। अपनी सीमित परपोषी रेंज और आनुवंशिक विविधता की कमी के कारण इन्फ्लूएंजा सी मानव में महामारी का कारण नहीं बन पाया है।[८]
इन्फ्लूएंजा ए
शूकर इन्फ्लूएंजा, इन्फ्लूएंजा ए के उपप्रकार एच1एन1,[९]एच1एन2,[९]एच3एन1,[१०]एच3एन2,[९] और एच2एन3.[११] के कारण होता है। पूरे विश्व मे सूअरों में, तीन इन्फ्लूएंजा ए विषाणु उपप्रकार एच1एन1, एच3एन2 और एच1एन2 सबसे आम हैं।
पृष्ठभूमि
एच१एन१ स्पैनिश फ्लु से आया, जो १९१८ और १९१९ के दौरान फैली एक महामारी थी जिससे लगभग ५ करोड़ लोग मारे गए थे। [१२] जो वायरस स्पैनिश फ्लु से आया वह सूअरों में विद्यमान रहा। इसका संचलन २० वीं सदी के दौरान मनुष्यों में भी हुआ, यद्यपि यह वर्ष के उस समय होता है जब प्रतिवर्ष होने वाली महामारियाँ फैलती हैं, जिससे 'सामान्य' इंफ्लुएंजा और शूकर इंफ्लुएंजा में अंतर कर पाना कठिन है। हालांकि सुअरों से मनुष्यों में होने वाले संक्रमण के मामले बहुत विरल हैं, और २००५ के बाद से अमेरिका में १२ मामले पाए गए हैं।[१३]
शूकर इंफ्लुएंजा कहाँ पाया जाता है
मनुष्यों में शूकर इंफ्लुएंजा
२००९ का फैलाव
 |
बचाव
- हर किसी को अपना मुँह और अपनी नाक ढक कर रखना जरूरी है, खासकर तब जब कोई छींक रहा हो;
- बार-बार हाथ धोना जरूरी है;
- अगर किसी को ऐसा लगता है कि उनकी तबीयत ठीक नहीं है तो उन्हें घर पर रहना चाहिये। ऐसी स्थिति में काम या स्कूल पर जाना उचित नहीं होगा और जहां तक हो सके भीड़ से दूर रहना फायदेमंद साबित होगा।
- अगर सांस लेने में तकलीफ होती है, या फिर अचानक चक्कर आने लगते हैं, या उल्टी होने लगती है तो ऐसे हालात में फ़ौरन डॉक्टर के पास जाना जरूरी है.
शूकर इन्फ्लूएंजा
शूकर इन्फ्लूएंजा, जिसे एच1एन1 या स्वाइन फ्लू भी कहते हैं, विभिन्न शूकर इन्फ्लूएंजा विषाणुओं मे से किसी एक के द्वारा फैलाया गया संक्रमण है। शूकर इन्फ्लूएंजा विषाणु (SIV-एस.आई.वी), इन्फ्लूएंजा कुल के विषाणुओं का वह कोई भी उपभेद है, जो कि सूअरों की स्थानिकमारी के लिए उत्तरदायी है।[२] 2009 तक ज्ञात एस.आई.वी उपभेदों में इन्फ्लूएंजा सी और इन्फ्लूएंजा ए के उपप्रकार एच1एन1 (H1N1), एच1एन2 (H1N2), एच3एन1 (H3N1), एच3एन2 (H3N2) और एच2एन3 (H2N3) शामिल हैं। इस प्रकार का इन्फ्लूएंजा मनुष्यों और पक्षियों पर भी प्रभाव डालता है।
शूकर इन्फ्लूएंजा विषाणु का दुनिया भर के सुअरो मे पाया जाना आम है। इस विषाणु का सूअरों से मनुष्य मे संचरण आम नहीं है और हमेशा ही यह विषाणु मानव इन्फ्लूएंजा का कारण नहीं बनता, अक्सर रक्त में इसके विरुद्ध सिर्फ प्रतिपिंडों (एंटीबॉडी) का उत्पादन ही होता है। यदि इसका संचरण, मानव इन्फ्लूएंजा का कारण बनता है, तब इसे ज़ूनोटिक शूकर इन्फ्लूएंजा कहा जाता है। जो व्यक्ति नियमित रूप से सूअरों के सम्पर्क में रहते है उन्हें इस फ्लू के संक्रमण का जोखिम अधिक होता है। यदि एक संक्रमित सुअर का मांस ठीक से पकाया जाये तो इसके सेवन से संक्रमण का कोई खतरा नहीं होता।
२०वीं शताब्दी के मध्य मे, इन्फ्लूएंजा के उपप्रकारों की पहचान संभव हो गयी जिसके कारण, मानव मे इसके संचरण का सही निदान संभव हो पाया। तब से ऐसे केवल ५० संचरणों की पुष्टि की गई है। शूकर इन्फ्लूएंजा के यह उपभेद बिरले ही एक मानव से दूसरे मानव मे संचारित होते हैं। मानव में ज़ूनोटिक शूकर इन्फ्लूएंजा के लक्षण आम इन्फ्लूएंजा के लक्षणों के समान ही होते हैं, जैसे ठंड लगना, बुखार, गले में ख़राश, खाँसी, मांसपेशियों में दर्द, तेज सिर दर्द, कमजोरी और सामान्य बेचैनी।
[संपादित करें] चिन्ह व लक्षण
[संपादित करें] सूअर में
सूअरों में इन्फ्लूएंजा संक्रमण के कारण ज्वर, सुस्ती, छींक, खाँसी, साँस लेने में कठिनाई, और भूख की कमी हो सकती है। कुछ मामलों में यह संक्रमण गर्भपात का कारण बन सकता है। हालांकि आमतौर पर मृत्यु सिर्फ 1-4% मामलों मे ही होती है। यह संक्रमण सूअर का वजन घटा और विकास को प्रभावित कर सकता है जो इनके पालको के आर्थिक नुकसान का कारण बन सकता है। संक्रमित सूअर का वजन 3 से 4 सप्ताह की अवधि के दौरान ५ से ६ किलोग्राम तक घट सकता है।
[संपादित करें] मनुष्यों में
यह भी देखें: The Centers for Disease Control and Prevention (CDC): Symptoms of Swine Flu in YouTube
मनुष्यों में शूकर इन्फ्लूएंजा का मुख्य लक्षण हैं: -
- ज्वर
- गले मे खरांश
- जुकाम
- खाँसी
- सिर व बदन दर्द
- जोड़ों में कठोरता
- उल्टी
- मूर्छा
- ठंड लगना
शूकर इन्फ्लूएंजा विषाणु का संचरण सीधे सूअरों से मनुष्यों मे कभी कभी संभव है, इस स्थित मे इसे जू़नोटिक शूकर इन्फ्लूएंजा कहा जाता है। 1958 से अभी तक सिर्फ 50 मामले ही रिपोर्ट हुये हैं जिनमे से सिर्फ ६ व्यक्तियों की ही मृत्यु हुई है। इन छह लोगों में से एक महिला गर्भवती थी, एक को ल्यूकिमिया था, एक को हॉजकिन रोग था और दो लोग पहले से स्वस्थ थे। भले ही यह प्रत्यक्ष मामले बहुत कम लगें पर वास्तविक संक्रमण की सही दर कहीं अधिक हो सकती है, क्योंकि ज्यादातर मामलों मे यह सामान्य रोग ही लगता है, और इस कारण इसे रिपोर्ट ही नहीं किया जाता।
[संपादित करें] वर्गीकरण
तीन वंशो के इन्फ्लूएंजा विषाणु जो कि मानव इन्फ्लूएंजा के लिए उत्तरदायी हैं मे से दो सूअरों में भी इन्फ्लूएंजा फैला सकते हैं, जिसमे से इन्फ्लूएंजा ए तो बहुत आम है पर इन्फ्लूएंजा सी यदा कदा ही पाया जाता है।[४]अभी तक इन्फ्लूएंजा बी को सूअरों में देखा नहीं गया है। इन्फ्लूएंजा ए और इन्फ्लूएंजा सी के भीतर मनुष्य और सूअरों में पाये जाने वाले उपभेद भिन्न होते हैं हालांकि रीअसोर्टमेंट के कारण उपभेदों मे बड़े पैमाने जीन का स्थानांतरण देखा गया है चाहें यह सूअर, पक्षी या मानव प्रजाति में उपस्थित हो।
[संपादित करें] इन्फ्लूएंजा सी
इन्फ्लूएंजा सी विषाणु, मानव और सूअरों दोनों को संक्रमित करता है लेकिन इसका संक्रमण पक्षियों मे नहीं होता।[५] अतीत मे भी इसका संचरण सूअरों और इंसानों के बीच हुआ है।[६]उदाहरण के लिए, इन्फ्लूएंजा सी के कारण जापान[७] और कैलिफोर्निया[७] में बच्चों के बीच इन्फ्लूएंजा का कम प्रभावी प्रकार फैला था। अपनी सीमित परपोषी रेंज और आनुवंशिक विविधता की कमी के कारण इन्फ्लूएंजा सी मानव में महामारी का कारण नहीं बन पाया है।[८]
[संपादित करें] इन्फ्लूएंजा ए
शूकर इन्फ्लूएंजा, इन्फ्लूएंजा ए के उपप्रकार एच1एन1,[९]एच1एन2,[९]एच3एन1,[१०]एच3एन2,[९] और एच2एन3.[११] के कारण होता है। पूरे विश्व मे सूअरों में, तीन इन्फ्लूएंजा ए विषाणु उपप्रकार एच1एन1, एच3एन2 और एच1एन2 सबसे आम हैं।
[संपादित करें] पृष्ठभूमि
एच१एन१ स्पैनिश फ्लु से आया, जो १९१८ और १९१९ के दौरान फैली एक महामारी थी जिससे लगभग ५ करोड़ लोग मारे गए थे। [१२] जो वायरस स्पैनिश फ्लु से आया वह सूअरों में विद्यमान रहा। इसका संचलन २० वीं सदी के दौरान मनुष्यों में भी हुआ, यद्यपि यह वर्ष के उस समय होता है जब प्रतिवर्ष होने वाली महामारियाँ फैलती हैं, जिससे 'सामान्य' इंफ्लुएंजा और शूकर इंफ्लुएंजा में अंतर कर पाना कठिन है। हालांकि सुअरों से मनुष्यों में होने वाले संक्रमण के मामले बहुत विरल हैं, और २००५ के बाद से अमेरिका में १२ मामले पाए गए हैं।[१३]
[संपादित करें] शूकर इंफ्लुएंजा कहाँ पाया जाता है
[संपादित करें] मनुष्यों में शूकर इंफ्लुएंजा
[संपादित करें] २००९ का फैलाव
| इस लेख का यह प्रभाग एक चालू घटना का वर्णन करता है। इस प्रभाग पर दी गई जानकारी शीघ्र या कालांतर (निकट या सुदूर भविष्य) में बदल सकती हैं। |
[संपादित करें] बचाव
- हर किसी को अपना मुँह और अपनी नाक ढक कर रखना जरूरी है, खासकर तब जब कोई छींक रहा हो;
- बार-बार हाथ धोना जरूरी है;
- अगर किसी को ऐसा लगता है कि उनकी तबीयत ठीक नहीं है तो उन्हें घर पर रहना चाहिये। ऐसी स्थिति में काम या स्कूल पर जाना उचित नहीं होगा और जहां तक हो सके भीड़ से दूर रहना फायदेमंद साबित होगा।
- अगर सांस लेने में तकलीफ होती है, या फिर अचानक चक्कर आने लगते हैं, या उल्टी होने लगती है तो ऐसे हालात में फ़ौरन डॉक्टर के पास जाना जरूरी है.
जानिए स्वाइन फ्लू के बारे में
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पेश है मनुष्यों के लिए नई इस बिमारी के बारे में जानकारी:
स्वाइन फ्लू है क्या?
स्वाइन फ्लू सूअर से उत्परिवर्तित वाईरस से हुई है. इसके लक्षण सामान्य फ्लू जैसे ही होते हैं, जैसे कि बूखार, गला सूखना, खाँसी आना, सरदर्द, नाक में खुजली होना, शरीर में दर्द आदि.
क्या इसका उपचार सम्भव है?
हाँ, कुछ दवाईयों ने इस बिमारी से ग्रस्त रोगियों पर असर दिखाया है. कुछ एंटिवाइरल दवाईयाँ भी कारगर सिद्ध हुई हैं. टेमिफ्लू तथा रेलेंज़ा जैसी दवाईयाँ असरकारक है.
क्या सुअरों से यह बिमारी फैल रही है?
शुरूआती लक्षण इस ओर इशारा करते जरूर हैं, लेकिन स्वाइन फ्लू इस समय इंसान से इंसान को लग रही है. यह बिमारी सुअरों में आम तौर पर पाई जाने वाली स्वाइन फ्लू का उत्परिवर्तित रूप कही जा सकती है.
स्वाइन फ्लू का वाइरस उत्परिवर्तित होता रहता है. इसका वही रूप इंसानों को लगा है, और अब इंसानों से ही फैल रहा है.
क्या सूअर का मांस घातक है?
नहीं! स्वाइन फ्लू खाने से नहीं फैलता. सूअर का मांस स्वाइन फ्लू के लिहाज से सुरक्षित है.
क्या सावधानियाँ रखनी चाहिए?
यदि कोई आपका परिचित अमरिका, मैक्सिको या यूरोप से आया है तो उसकी चिकित्सकीय जाँच कराएँ. यदि आप विदेश यात्रा पर जा रहे हैं तो सावधारी रखें.
बार बार हाथ धोते रहें. यदि आप बिमार महसूस कर रहे हैं तो घर पर ही रहें और खांसी को काबू में रखने का प्रयत्न करें. खांसते समय मूँह ढक लें. यदि खांसते समय हाथों से मूँह ढका है तो लगातार हाथ धोते रहें.
Wednesday, August 12, 2009
जाग्रत करें स्वयं का विवेक
पूर्णिमा की रात्रि थी शुभ्र ज्योत्सना में सारी पृथ्वी डूबी हुई थी। शंकर और पार्वती भी अपने प्यारे नंदी पर सवार होकर भ्रमण पर निकले हुए थे किंतु वे जैसे ही थोड़े आगे गए थे कुछ लोग उन्हें मार्ग में मिले। उन्हें नंदी पर बैठे देखकर उन लोगों ने कहा 'देखो तो इनके बैल में जान में जान नहीं है और दो-दो उस पर चढ़कर बैठे हैं।'
उनकी बात सुनकर पार्वती नीचे उतर गईं और पैदल चलने लगीं किंतु थोड़ी दूर चलने के बाद फिर कुछ लोग मिले। वे बोले 'अरे मजा तो देखो सुकुमार अबला को पैदल चलाकर यह कौन बैल पर बैठा जा रहा है भाई! बेशर्मी की भी हद है!' यह सुनकर शंकर नीचे उतर आए और पार्वती को नंदी पर बैठा दिया, लेकिन कुछ ही कदम गए होंगे कि फिर कुछ लोगों ने कहा 'कैसी बेहया औरत है कि पति को पैदल चलाकर खुद बैल पर बैठी है। मित्रों कलयुग आ गया है।'
ऐसी स्थिति देखकर आखिर दोनों ही नंदी के साथ पैदल चलने लगे किंतु थोड़ी ही दूर न जा पाए होंगे कि लोगों ने कहा 'देखो मूर्खों को। इतना तगड़ा बैल साथ में है और ये पैदल चल रहे हैं।' अब तो बड़ी कठिनाई हो गई। शंकर और पार्वती को कुछ भी करने को शेष न रहा।
नंदी को एक वृक्ष के नीचे रोककर वे विचार करने लगे। अब तक नंदी चुप था। अब हँसा और बोला 'एक रास्ता है, मैं बताऊँ? अब आप दोनों मुझे अपने सिरों पर उठा लीजिए।' यह सुनते ही शंकर और पार्वती को होश आया और दोनों नंदी पर सवार हो गए। लोग फिर भी कुछ न कुछ कहते निकलते रहे।
असल में लोग बिना कुछ कहे निकल भी कैसे सकते हैं? अब शंकर और पार्वती चाँदनी की सैर का आनंद लूट रहे थे और भूल गए थे कि मार्ग पर अन्य लोग भी निकल रहे हैं।
जीवन में यदि कहीं पहुँचना हो तो राह में मिलने वाले प्रत्येक व्यक्ति की बात पर ध्यान देना आत्मघातक है। वस्तुत: जिस व्यक्ति की सलाह का कोई मू्ल्य है, वह कभी बिना माँगे सलाह देता ही नहीं है। और यह भी स्मरण रहे कि जो स्वयं के विवेक से नहीं चलता है, उसकी गति हवा के झोकों में उड़ते सूखे पत्तों की भाँति हो जाती है।
उनकी बात सुनकर पार्वती नीचे उतर गईं और पैदल चलने लगीं किंतु थोड़ी दूर चलने के बाद फिर कुछ लोग मिले। वे बोले 'अरे मजा तो देखो सुकुमार अबला को पैदल चलाकर यह कौन बैल पर बैठा जा रहा है भाई! बेशर्मी की भी हद है!' यह सुनकर शंकर नीचे उतर आए और पार्वती को नंदी पर बैठा दिया, लेकिन कुछ ही कदम गए होंगे कि फिर कुछ लोगों ने कहा 'कैसी बेहया औरत है कि पति को पैदल चलाकर खुद बैल पर बैठी है। मित्रों कलयुग आ गया है।'
ऐसी स्थिति देखकर आखिर दोनों ही नंदी के साथ पैदल चलने लगे किंतु थोड़ी ही दूर न जा पाए होंगे कि लोगों ने कहा 'देखो मूर्खों को। इतना तगड़ा बैल साथ में है और ये पैदल चल रहे हैं।' अब तो बड़ी कठिनाई हो गई। शंकर और पार्वती को कुछ भी करने को शेष न रहा।
नंदी को एक वृक्ष के नीचे रोककर वे विचार करने लगे। अब तक नंदी चुप था। अब हँसा और बोला 'एक रास्ता है, मैं बताऊँ? अब आप दोनों मुझे अपने सिरों पर उठा लीजिए।' यह सुनते ही शंकर और पार्वती को होश आया और दोनों नंदी पर सवार हो गए। लोग फिर भी कुछ न कुछ कहते निकलते रहे।
असल में लोग बिना कुछ कहे निकल भी कैसे सकते हैं? अब शंकर और पार्वती चाँदनी की सैर का आनंद लूट रहे थे और भूल गए थे कि मार्ग पर अन्य लोग भी निकल रहे हैं।
जीवन में यदि कहीं पहुँचना हो तो राह में मिलने वाले प्रत्येक व्यक्ति की बात पर ध्यान देना आत्मघातक है। वस्तुत: जिस व्यक्ति की सलाह का कोई मू्ल्य है, वह कभी बिना माँगे सलाह देता ही नहीं है। और यह भी स्मरण रहे कि जो स्वयं के विवेक से नहीं चलता है, उसकी गति हवा के झोकों में उड़ते सूखे पत्तों की भाँति हो जाती है।
Sunday, August 9, 2009
Software testing
Software Testing is an empirical investigation conducted to provide stakeholders with information about the quality of the product or service under test[1], with respect to the context in which it is intended to operate. Software Testing also provides an objective, independent view of the software to allow the business to appreciate and understand the risks at implementation of the software. Test techniques include, but are not limited to, the process of executing a program or application with the intent of finding software bugs. Software Testing can also be stated as the process of validating and verifying that a software program/application/product (1) meets the business and technical requirements that guided its design and development; (2) works as expected; and (3) can be implemented with the same characteristics.
Software Testing, depending on the testing method employed, can be implemented at any time in the development process, however most of the test effort occurs after the requirements have been defined and the coding process has been completed.
Contents |
Overview
Testing can never completely identify all the defects within software. Instead, it furnishes a criticism or comparison that compares the state and behavior of the product against oracles—principles or mechanisms by which someone might recognize a problem. These oracles may include (but are not limited to) specifications, contracts[2], comparable products, past versions of the same product, inferences about intended or expected purpose, user or customer expectations, relevant standards, applicable laws, or other criteria.
Every software product has a target audience. For example, the audience for video game software is completely different from banking software. Therefore, when an organization develops or otherwise invests in a software product, it can assess whether the software product will be acceptable to its end users, its target audience, its purchasers, and other stakeholders. Software testing is the process of attempting to make this assessment.
A study conducted by NIST in 2002 reports that software bugs cost the U.S. economy $59.5 billion annually. More than a third of this cost could be avoided if better software testing was performed.[3]
History
The separation of debugging from testing was initially introduced by Glenford J. Myers in 1979.[4] Although his attention was on breakage testing ("a successful test is one that finds a bug"[4][5]), it illustrated the desire of the software engineering community to separate fundamental development activities, such as debugging, from that of verification. Dave Gelperin and William C. Hetzel classified in 1988 the phases and goals in software testing in the following stages:[6]
- Until 1956 - Debugging oriented[7]
- 1957–1978 - Demonstration oriented[8]
- 1979–1982 - Destruction oriented[9]
- 1983–1987 - Evaluation oriented[10]
- 1988–2000 - Prevention oriented[11]
Software testing topics
Scope
A primary purpose for testing is to detect software failures so that defects may be uncovered and corrected. This is a non-trivial pursuit. Testing cannot establish that a product functions properly under all conditions but can only establish that it does not function properly under specific conditions.[12] The scope of software testing often includes examination of code as well as execution of that code in various environments and conditions as well as examining the aspects of code: does it do what it is supposed to do and do what it needs to do. In the current culture of software development, a testing organization may be separate from the development team. There are various roles for testing team members. Information derived from software testing may be used to correct the process by which software is developed[13].
Defects and failures
Not all software defects are caused by coding errors. One common source of expensive defects is caused by requirement gaps, e.g., unrecognized requirements, that result in errors of omission by the program designer[14]. A common source of requirements gaps is non-functional requirements such as testability, scalability, maintainability, usability, performance, and security.
Software faults occur through the following processes. A programmer makes an error (mistake), which results in a defect (fault, bug) in the software source code. If this defect is executed, in certain situations the system will produce wrong results, causing a failure.[15] Not all defects will necessarily result in failures. For example, defects in dead code will never result in failures. A defect can turn into a failure when the environment is changed. Examples of these changes in environment include the software being run on a new hardware platform, alterations in source data or interacting with different software.[15] A single defect may result in a wide range of failure symptoms.
Compatibility
A frequent cause of software failure is compatibility with another application, a new operating system, or, increasingly, web browser version. In the case of lack of backward compatibility, this can occur (for example...) because the programmers have only considered coding their programs for, or testing the software upon, "the latest version of" this-or-that operating system. The unintended consequence of this fact is that: their latest work might not be fully compatible with earlier mixtures of software/hardware, or it might not be fully compatible with another important operating system. In any case, these differences, whatever they might be, may have resulted in (unintended...) software failures, as witnessed by some significant population of computer users.
This could be considered a "prevention oriented strategy" that fits well with the latest testing phase suggested by Dave Gelperin and William C. Hetzel, as cited below [11].
Input combinations and preconditions
A very fundamental problem with software testing is that testing under all combinations of inputs and preconditions (initial state) is not feasible, even with a simple product.[12][16] This means that the number of defects in a software product can be very large and defects that occur infrequently are difficult to find in testing. More significantly, non-functional dimensions of quality (how it is supposed to be versus what it is supposed to do)—usability, scalability, performance, compatibility, reliability—can be highly subjective; something that constitutes sufficient value to one person may be intolerable to another.
Static vs. dynamic testing
There are many approaches to software testing. Reviews, walkthroughs, or inspections are considered as static testing, whereas actually executing programmed code with a given set of test cases is referred to as dynamic testing. Static testing can be (and unfortunately in practice often is) omitted. Dynamic testing takes place when the program itself is used for the first time (which is generally considered the beginning of the testing stage). Dynamic testing may begin before the program is 100% complete in order to test particular sections of code (modules or discrete functions). Typical techniques for this are either using stubs/drivers or execution from a debugger environment. For example, Spreadsheet programs are, by their very nature, tested to a large extent interactively ("on the fly"), with results displayed immediately after each calculation or text manipulation.
Software verification and validation
Software testing is used in association with verification and validation:[17]
- Verification: Have we built the software right? (i.e., does it match the specification).
- Validation: Have we built the right software? (i.e., is this what the customer wants).
The terms verification and validation are commonly used interchangeably in the industry; it is also common to see these two terms incorrectly defined. According to the IEEE Standard Glossary of Software Engineering Terminology:
- Verification is the process of evaluating a system or component to determine whether the products of a given development phase satisfy the conditions imposed at the start of that phase.
- Validation is the process of evaluating a system or component during or at the end of the development process to determine whether it satisfies specified requirements.
The software testing team
Software testing can be done by software testers. Until the 1980s the term "software tester" was used generally, but later it was also seen as a separate profession. Regarding the periods and the different goals in software testing[18], different roles have been established: manager, test lead, test designer, tester, automation developer, and test administrator.
Software Quality Assurance (SQA)
Though controversial, software testing may be viewed as an important part of the software quality assurance (SQA) process.[12] In SQA, software process specialists and auditors take a broader view on software and its development. They examine and change the software engineering process itself to reduce the amount of faults that end up in the delivered software: the so-called defect rate.
What constitutes an "acceptable defect rate" depends on the nature of the software. For example, an arcade video game designed to simulate flying an airplane would presumably have a much higher tolerance for defects than mission critical software such as that used to control the functions of an airliner that really is flying!
Although there are close links with SQA, testing departments often exist independently, and there may be no SQA function in some companies.
Software Testing is a task intended to detect defects in software by contrasting a computer program's expected results with its actual results for a given set of inputs. By contrast, QA (Quality Assurance) is the implementation of policies and procedures intended to prevent defects from occurring in the first place.
Testing methods
Approach of boxes
Software testing methods are traditionally divided into black box testing and white box testing. These two approaches are used to describe the point of view that a test engineer takes when designing test cases.
Black box testing
Black box testing treats the software as a "black box"—without any knowledge of internal implementation. Black box testing methods include: equivalence partitioning, boundary value analysis, all-pairs testing, fuzz testing, model-based testing, traceability matrix, exploratory testing and specification-based testing.
- Specification-based testing: Specification-based testing aims to test the functionality of software according to the applicable requirements.[19] Thus, the tester inputs data into, and only sees the output from, the test object. This level of testing usually requires thorough test cases to be provided to the tester, who then can simply verify that for a given input, the output value (or behavior), either "is" or "is not" the same as the expected value specified in the test case.
- Specification-based testing is necessary, but it is insufficient to guard against certain risks.[20]
- Advantages and disadvantages: The black box tester has no "bonds" with the code, and a tester's perception is very simple: a code must have bugs. Using the principle, "Ask and you shall receive," black box testers find bugs where programmers do not. But, on the other hand, black box testing has been said to be "like a walk in a dark labyrinth without a flashlight," because the tester doesn't know how the software being tested was actually constructed. As a result, there are situations when (1) a tester writes many test cases to check something that could have been tested by only one test case, and/or (2) some parts of the back-end are not tested at all.
Therefore, black box testing has the advantage of "an unaffiliated opinion," on the one hand, and the disadvantage of "blind exploring," on the other. [21]
White box testing
White box testing is when the tester has access to the internal data structures and algorithms including the code that implement these.
- Types of white box testing
- The following types of white box testing exist:
- API testing (application programming interface) - Testing of the application using Public and Private APIs
- Code coverage - creating tests to satisfy some criteria of code coverage (e.g., the test designer can create tests to cause all statements in the program to be executed at least once)
- Fault injection methods
- Mutation testing methods
- Static testing - White box testing includes all static testing
- Code completeness evaluation
- White box testing methods can also be used to evaluate the completeness of a test suite that was created with black box testing methods. This allows the software team to examine parts of a system that are rarely tested and ensures that the most important function points have been tested.[22]
- Two common forms of code coverage are:
- Function coverage, which reports on functions executed
- Statement coverage, which reports on the number of lines executed to complete the test
They both return a code coverage metric, measured as a percentage.
Grey Box Testing
Grey box testing involves having access to internal data structures and algorithms for purposes of designing the test cases, but testing at the user, or black-box level. Manipulating input data and formatting output do not qualify as grey box, because the input and output are clearly outside of the "black-box" that we are calling the system under test. This distinction is particularly important when conducting integration testing between two modules of code written by two different developers, where only the interfaces are exposed for test. However, modifying a data repository does qualify as grey box, as the user would not normally be able to change the data outside of the system under test. Grey box testing may also include reverse engineering to determine, for instance, boundary values or error messages.
Integration Testing
Regression Testing
Acceptance testing
Acceptance testing can mean one of two things:
- A smoke test is used as an acceptance test prior to introducing a new build to the main testing process, i.e. before integration or regression.
- Acceptance testing performed by the customer, often in their lab environment on their own HW, is known as user acceptance testing (UAT).
Non Functional Software Testing
Special methods exist to test non-functional aspects of software.
- Performance testing checks to see if the software can handle large quantities of data or users. This is generally referred to as software scalability. This activity of Non Functional Software Testing is often referred to as Endurance Testing.
- Stability testing checks to see if the software can continuously function well in or above an acceptable period. This activity of Non Functional Software Testing is oftentimes referred to as load (or endurance) testing.
- Usability testing is needed to check if the user interface is easy to use and understand.
- Security testing is essential for software that processes confidential data to prevent system intrusion by hackers.
- Internationalization and localization is needed to test these aspects of software, for which a pseudolocalization method can be used.
In contrast to functional testing, which establishes the correct operation of the software (correct in that it matches the expected behavior defined in the design requirements), non-functional testing verifies that the software functions properly even when it receives invalid or unexpected inputs. Software fault injection, in the form of fuzzing, is an example of non-functional testing. Non-functional testing, especially for software, is designed to establish whether the device under test can tolerate invalid or unexpected inputs, thereby establishing the robustness of input validation routines as well as error-handling routines. Various commercial non-functional testing tools are linked from the Software fault injection page; there are also numerous open-source and free software tools available that perform non-functional testing..
Destructive testing
Destructive testing attempts to cause the software or a sub-system to fail, in order to test its robustness.
Testing process
A common practice of software testing is performed by an independent group of testers after the functionality is developed before it is shipped to the customer.[23] This practice often results in the testing phase being used as project buffer to compensate for project delays, thereby compromising the time devoted to testing.[24] Another practice is to start software testing at the same moment the project starts and it is a continuous process until the project finishes.[25]
In counterpoint, some emerging software disciplines such as extreme programming and the agile software development movement, adhere to a "test-driven software development" model. In this process, unit tests are written first, by the software engineers (often with pair programming in the extreme programming methodology). Of course these tests fail initially; as they are expected to. Then as code is written it passes incrementally larger portions of the test suites. The test suites are continuously updated as new failure conditions and corner cases are discovered, and they are integrated with any regression tests that are developed. Unit tests are maintained along with the rest of the software source code and generally integrated into the build process (with inherently interactive tests being relegated to a partially manual build acceptance process).
Testing can be done on the following levels:
- Unit testing tests the minimal software component, or module. Each unit (basic component) of the software is tested to verify that the detailed design for the unit has been correctly implemented. In an object-oriented environment, this is usually at the class level, and the minimal unit tests include the constructors and destructors.[26]
- Integration testing exposes defects in the interfaces and interaction between integrated components (modules). Progressively larger groups of tested software components corresponding to elements of the architectural design are integrated and tested until the software works as a system. [27]
- System testing tests a completely integrated system to verify that it meets its requirements.[28]
- System integration testing verifies that a system is integrated to any external or third party systems defined in the system requirements.[citation needed]
Before shipping the final version of software, alpha and beta testing are often done additionally:
- Alpha testing is simulated or actual operational testing by potential users/customers or an independent test team at the developers' site. Alpha testing is often employed for off-the-shelf software as a form of internal acceptance testing, before the software goes to beta testing.[citation needed]
- Beta testing comes after alpha testing. Versions of the software, known as beta versions, are released to a limited audience outside of the programming team. The software is released to groups of people so that further testing can ensure the product has few faults or bugs. Sometimes, beta versions are made available to the open public to increase the feedback field to a maximal number of future users.[citation needed]
Finally, acceptance testing can be conducted by the end-user, customer, or client to validate whether or not to accept the product. Acceptance testing may be performed as part of the hand-off process between any two phases of development.[citation needed]
Regression testing
After modifying software, either for a change in functionality or to fix defects, a regression test re-runs previously passing tests on the modified software to ensure that the modifications have not unintentionally caused a regression of previous functionality. Regression testing can be performed at any or all of the above test levels. These regression tests are often automated.
More specific forms of regression testing are known as sanity testing (which quickly checks for bizarre behavior) and smoke testing (which tests for basic functionality).
Benchmarks may be employed during regression testing to ensure that the performance of the newly modified software will be at least as acceptable as the earlier version or, in the case of code optimization, that some real improvement has been achieved.
Finding faults
Finding faults early
It is commonly believed that the earlier a defect is found the cheaper it is to fix it.[29] The following table shows the cost of fixing the defect depending on the stage it was found.[30] For example, if a problem in the requirements is found only post-release, then it would cost 10–100 times more to fix than if it had already been found by the requirements review.
-
Time Detected Requirements Architecture Construction System Test Post-Release Time Introduced Requirements 1× 3× 5–10× 10× 10–100× Architecture - 1× 10× 15× 25–100× Construction - - 1× 10× 10–25×
[edit] Testing Tools
Program testing and fault detection can be aided significantly by testing tools and debuggers. Testing/debug tools include features such as:
- Program monitors, permitting full or partial monitoring of program code including:
- Instruction Set Simulator, permitting complete instruction level monitoring and trace facilities
- Program animation, permitting step-by-step execution and conditional breakpoint at source level or in machine code
- Code coverage reports
- Formatted dump or Symbolic debugging, tools allowing inspection of program variables on error or at chosen points
- Automated functional GUI testing tools are used to repeat system-level tests through the GUI
- Benchmarks, allowing run-time performance comparisons to be made
- Performance analysis (or profiling tools) that can help to highlight hot spots and resource usage
Some of these features may be incorporated into an Integrated Development Environment (IDE).
[edit] Measuring software testing
Usually, quality is constrained to such topics as correctness, completeness, security,[citation needed] but can also include more technical requirements as described under the ISO standard ISO 9126, such as capability, reliability, efficiency, portability, maintainability, compatibility, and usability.
There are a number of common software measures, often called "metrics", which are used to measure the state of the software or the adequacy of the testing.
[edit] Testing artifacts
Software testing process can produce several artifacts.
- Test plan
- A test specification is called a test plan. The developers are well aware what test plans will be executed and this information is made available to management and the developers. The idea is makes them more cautious when developing their code or making additional changes. Some companies have a higher-level document called a test strategy.
- Traceability matrix
- A traceability matrix is a table that correlates requirements or design documents to test documents. It is used to change tests when the source documents are changed, or to verify that the test results are correct.
- Test case
- A test case normally consists of a unique identifier, requirement references from a design specification, preconditions, events, a series of steps (also known as actions) to follow, input, output, expected result, and actual result. Clinically defined a test case is an input and an expected result.[31] This can be as pragmatic as 'for condition x your derived result is y', whereas other test cases described in more detail the input scenario and what results might be expected. It can occasionally be a series of steps (but often steps are contained in a separate test procedure that can be exercised against multiple test cases, as a matter of economy) but with one expected result or expected outcome. The optional fields are a test case ID, test step, or order of execution number, related requirement(s), depth, test category, author, and check boxes for whether the test is automatable and has been automated. Larger test cases may also contain prerequisite states or steps, and descriptions. A test case should also contain a place for the actual result. These steps can be stored in a word processor document, spreadsheet, database, or other common repository. In a database system, you may also be able to see past test results, who generated the results, and what system configuration was used to generate those results. These past results would usually be stored in a separate table.
- Test script
- The test script is the combination of a test case, test procedure, and test data. Initially the term was derived from the product of work created by automated regression test tools. Today, test scripts can be manual, automated, or a combination of both.
- Test suite
- The most common term for a collection of test cases is a test suite. The test suite often also contains more detailed instructions or goals for each collection of test cases. It definitely contains a section where the tester identifies the system configuration used during testing. A group of test cases may also contain prerequisite states or steps, and descriptions of the following tests.
- Test data
- In most cases, multiple sets of values or data are used to test the same functionality of a particular feature. All the test values and changeable environmental components are collected in separate files and stored as test data. It is also useful to provide this data to the client and with the product or a project.
- Test harness
- The software, tools, samples of data input and output, and configurations are all referred to collectively as a test harness.
[edit] A sample testing cycle
Although variations exist between organizations, there is a typical cycle for testing[32]:
- Requirements analysis: Testing should begin in the requirements phase of the software development life cycle. During the design phase, testers work with developers in determining what aspects of a design are testable and with what parameters those tests work.
- Test planning: Test strategy, test plan, testbed creation. Since many activities will be carried out during testing, a plan is needed.
- Test development: Test procedures, test scenarios, test cases, test datasets, test scripts to use in testing software.
- Test execution: Testers execute the software based on the plans and tests and report any errors found to the development team.
- Test reporting: Once testing is completed, testers generate metrics and make final reports on their test effort and whether or not the software tested is ready for release.
- Test result analysis: Or Defect Analysis, is done by the development team usually along with the client, in order to decide what defects should be treated, fixed, rejected (i.e. found software working properly) or deferred to be dealt with later.
- Defect Retesting: Once a defect has been dealt with by the development team, it is retested by the testing team.
- Regression testing: It is common to have a small test program built of a subset of tests, for each integration of new, modified, or fixed software, in order to ensure that the latest delivery has not ruined anything, and that the software product as a whole is still working correctly.
- Test Closure: Once the test meets the exit criteria, the activities such as capturing the key outputs, lessons learned, results, logs, documents related to the project are archived and used as a reference for future projects.
[edit] Certifications
Several certification programs exist to support the professional aspirations of software testers and quality assurance specialists. No certification currently offered actually requires the applicant to demonstrate the ability to test software. No certification is based on a widely accepted body of knowledge. This has led some to declare that the testing field is not ready for certification.[33] Certification itself cannot measure an individual's productivity, their skill, or practical knowledge, and cannot guarantee their competence, or professionalism as a tester.[34]
- Software testing certification types
- Testing certifications
-
- CATe offered by the International Institute for Software Testing[35]
- Certified Software Tester (CSTE) offered by the Quality Assurance Institute (QAI)[36]
- Certified Software Test Professional (CSTP) offered by the International Institute for Software Testing[35]
- CSTP (TM) (Australian Version) offered by K. J. Ross & Associates[37]
- ISEB offered by the Information Systems Examinations Board
- ISTQB Certified Tester, Foundation Level (CTFL) offered by the International Software Testing Qualification Board [38][39]
- ISTQB Certified Tester, Advanced Level (CTAL) offered by the International Software Testing Qualification Board [38][39]
- TMPF TMap[dubious ] Next Foundation offered by the Examination Institute for Information Science[40]
- Quality assurance certifications
-
- CSQE offered by the American Society for Quality (ASQ)[41]
- CSQA offered by the Quality Assurance Institute (QAI)[36]
- CQIA offered by the American Society for Quality (ASQ)[41]
- CMSQ offered by the Quality Assurance Institute (QAI)[42]
[edit] Controversy
Some of the major software testing controversies include:
- What constitutes responsible software testing?
- Members of the "context-driven" school of testing[43] believe that there are no "best practices" of testing, but rather that testing is a set of skills that allow the tester to select or invent testing practices to suit each unique situation. [44]
- Agile vs. traditional
- Should testers learn to work under conditions of uncertainty and constant change or should they aim at process "maturity"? The agile testing movement has received growing popularity since 2006 mainly in commercial circles [45], whereas government and military software providers are slow to embrace this methodology[neutrality disputed], and mostly still hold to CMMI.[46]
- Exploratory test vs. scripted[47]
- Should tests be designed at the same time as they are executed or should they be designed beforehand?
- Manual testing vs. automated
- Some writers believe that test automation is so expensive relative to its value that it should be used sparingly.[48] Others, such as advocates of agile development, recommend automating 100% of all tests.[citation needed] More in particular, test-driven development states that developers should write unit-tests of the XUnit type before coding the functionality. The tests then can be considered as a way to capture and implement the requirements.
- Software design vs. software implementation[49]
- Should testing be carried out only at the end or throughout the whole process?
- Who watches the watchmen?
- The idea is that any form of observation is also an interaction—the act of testing can also affect that which is being tested[50]
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